1 files changed, 77 insertions, 39 deletions

diff --git a/mm/gup.c b/mm/gup.c
index 4637dab7b54f..ad0c8922dac3 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2273,20 +2273,57 @@ struct page *get_dump_page(unsigned long addr)
 #endif /* CONFIG_ELF_CORE */
 
 #ifdef CONFIG_MIGRATION
+
+/*
+ * An array of either pages or folios ("pofs"). Although it may seem tempting to
+ * avoid this complication, by simply interpreting a list of folios as a list of
+ * pages, that approach won't work in the longer term, because eventually the
+ * layouts of struct page and struct folio will become completely different.
+ * Furthermore, this pof approach avoids excessive page_folio() calls.
+ */
+struct pages_or_folios {
+	union {
+		struct page **pages;
+		struct folio **folios;
+		void **entries;
+	};
+	bool has_folios;
+	long nr_entries;
+};
+
+static struct folio *pofs_get_folio(struct pages_or_folios *pofs, long i)
+{
+	if (pofs->has_folios)
+		return pofs->folios[i];
+	return page_folio(pofs->pages[i]);
+}
+
+static void pofs_clear_entry(struct pages_or_folios *pofs, long i)
+{
+	pofs->entries[i] = NULL;
+}
+
+static void pofs_unpin(struct pages_or_folios *pofs)
+{
+	if (pofs->has_folios)
+		unpin_folios(pofs->folios, pofs->nr_entries);
+	else
+		unpin_user_pages(pofs->pages, pofs->nr_entries);
+}
+
 /*
  * Returns the number of collected folios. Return value is always >= 0.
  */
 static unsigned long collect_longterm_unpinnable_folios(
-					struct list_head *movable_folio_list,
-					unsigned long nr_folios,
-					struct folio **folios)
+		struct list_head *movable_folio_list,
+		struct pages_or_folios *pofs)
 {
 	unsigned long i, collected = 0;
 	struct folio *prev_folio = NULL;
 	bool drain_allow = true;
 
-	for (i = 0; i < nr_folios; i++) {
-		struct folio *folio = folios[i];
+	for (i = 0; i < pofs->nr_entries; i++) {
+		struct folio *folio = pofs_get_folio(pofs, i);
 
 		if (folio == prev_folio)
 			continue;
@@ -2327,16 +2364,15 @@ static unsigned long collect_longterm_unpinnable_folios(
  * Returns -EAGAIN if all folios were successfully migrated or -errno for
  * failure (or partial success).
  */
-static int migrate_longterm_unpinnable_folios(
-					struct list_head *movable_folio_list,
-					unsigned long nr_folios,
-					struct folio **folios)
+static int
+migrate_longterm_unpinnable_folios(struct list_head *movable_folio_list,
+				   struct pages_or_folios *pofs)
 {
 	int ret;
 	unsigned long i;
 
-	for (i = 0; i < nr_folios; i++) {
-		struct folio *folio = folios[i];
+	for (i = 0; i < pofs->nr_entries; i++) {
+		struct folio *folio = pofs_get_folio(pofs, i);
 
 		if (folio_is_device_coherent(folio)) {
 			/*
@@ -2344,7 +2380,7 @@ static int migrate_longterm_unpinnable_folios(
 			 * convert the pin on the source folio to a normal
 			 * reference.
 			 */
-			folios[i] = NULL;
+			pofs_clear_entry(pofs, i);
 			folio_get(folio);
 			gup_put_folio(folio, 1, FOLL_PIN);
 
@@ -2363,8 +2399,8 @@ static int migrate_longterm_unpinnable_folios(
 		 * calling folio_isolate_lru() which takes a reference so the
 		 * folio won't be freed if it's migrating.
 		 */
-		unpin_folio(folios[i]);
-		folios[i] = NULL;
+		unpin_folio(folio);
+		pofs_clear_entry(pofs, i);
 	}
 
 	if (!list_empty(movable_folio_list)) {
@@ -2387,12 +2423,26 @@ static int migrate_longterm_unpinnable_folios(
 	return -EAGAIN;
 
 err:
-	unpin_folios(folios, nr_folios);
+	pofs_unpin(pofs);
 	putback_movable_pages(movable_folio_list);
 
 	return ret;
 }
 
+static long
+check_and_migrate_movable_pages_or_folios(struct pages_or_folios *pofs)
+{
+	LIST_HEAD(movable_folio_list);
+	unsigned long collected;
+
+	collected = collect_longterm_unpinnable_folios(&movable_folio_list,
+						       pofs);
+	if (!collected)
+		return 0;
+
+	return migrate_longterm_unpinnable_folios(&movable_folio_list, pofs);
+}
+
 /*
  * Check whether all folios are *allowed* to be pinned indefinitely (long term).
  * Rather confusingly, all folios in the range are required to be pinned via
@@ -2417,16 +2467,13 @@ err:
 static long check_and_migrate_movable_folios(unsigned long nr_folios,
 					     struct folio **folios)
 {
-	unsigned long collected;
-	LIST_HEAD(movable_folio_list);
+	struct pages_or_folios pofs = {
+		.folios = folios,
+		.has_folios = true,
+		.nr_entries = nr_folios,
+	};
 
-	collected = collect_longterm_unpinnable_folios(&movable_folio_list,
-						       nr_folios, folios);
-	if (!collected)
-		return 0;
-
-	return migrate_longterm_unpinnable_folios(&movable_folio_list,
-						  nr_folios, folios);
+	return check_and_migrate_movable_pages_or_folios(&pofs);
 }
 
 /*
@@ -2436,22 +2483,13 @@ static long check_and_migrate_movable_folios(unsigned long nr_folios,
 static long check_and_migrate_movable_pages(unsigned long nr_pages,
 					    struct page **pages)
 {
-	struct folio **folios;
-	long i, ret;
+	struct pages_or_folios pofs = {
+		.pages = pages,
+		.has_folios = false,
+		.nr_entries = nr_pages,
+	};
 
-	folios = kmalloc_array(nr_pages, sizeof(*folios), GFP_KERNEL);
-	if (!folios) {
-		unpin_user_pages(pages, nr_pages);
-		return -ENOMEM;
-	}
-
-	for (i = 0; i < nr_pages; i++)
-		folios[i] = page_folio(pages[i]);
-
-	ret = check_and_migrate_movable_folios(nr_pages, folios);
-
-	kfree(folios);
-	return ret;
+	return check_and_migrate_movable_pages_or_folios(&pofs);
 }
 #else
 static long check_and_migrate_movable_pages(unsigned long nr_pages,